Thread: Flagstone Discolouration Problem (severe)

This spring, I had a flagstone walkway installed in front of my house with grey and buff flagstone. Over the past month, they grey limestone has faded considerably, and the buff limestone has developed "rust" color throughout the whole walkway. The landscaper has not seen this problem in his 20 years of experience. Further photos are available.

You can almost see a path straight to your garage. Something to keep in mind with stone, it was taken from within the ground and now it is exposed to the elements. Rust is not uncommon in flagstone/variegated bluestone but is typically visible at the time of installation, not a development. You are likely introducing something to the stone, after it's installation, that is causing these irregularities. This is also assuming that NONE of it was there at installation as it can migrate. A cleaner isn't going to solve any problem you may have if you do not have the source of what is the cause. A sealer isn't going to stop staining but it will help prevent and make it easier to clean.

In addition to the above questions, are you on city water or do you have a well?

- we do not wash or park cars in the driveway.
- we do not leave a hose outside.
- the garage doors are vinyl.
- have not tried a rust remover.
- city water in Toronto
- it was just installed this spring, so nothing has touched the stone except air and rain.

I don't think that it has really formed a path from the garage, but will double check in the morning.

Could it be some kind of reaction with the base that it is sitting on ? I think that it is a concrete base, but will check.

Looking at the material, it seems to me to be consistent with variation in natural stone. Variations in material are expensive to control. IE... selecting and approving each piece for the site. These stones look like they have more iron oxide content in them. Over time the color of your material will change due to the environment.
It does not look like a limestone to me.
Almost all of those stones seem to have similar characteristics. The stones in the second image exhibiting the strongest.
Basic oxidation. Get info from the supplier of the material to understand it better.
What is under the stones? Concrete with rebar or mesh for structure?

The stone gets pulled out of the ground (where it is not exposed to air) it is quickly stacked which again (does not allow much air to the stone). Only when the stone is installed and open to the air will you begin to see ferrous components to the stone in the way of rust colored deposits. It is part of the irregularities of dealing with natural stone. Frankly, I like the rust color that is weaved within the gray slate. It gives the stone more depth and character.

It doesnt have pigments added. It doesn't have paste mixed in. It will do what is called "wash out".

In our area, we have an old, historical, national park. Called Harpers Ferry (in WV). It's an old old town. lostsa stone buildings, stone walls, walks, etc. And all the stone has faded to a whitish color.

When I price stonework I always tell the client its gonna loose it's color.

When it comes to stone you have to understand 2 things:

1) its a product of mother nature
2) If it's mortared to a slab, it's subject to freezing and popping from the slab in the winter

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